Reflectance sensor for integral illuminant-weighted CIE color matching filters

Abstract

A tristimulus colorimeter for measuring reflective or transmissive materials is provided. The colorimeter measures a sample under a calibrated light source, receives inputs to detectors, and determines CIE tristimulus values of the same sample as they would occur under a reference light source. The colorimeter includes a calibrated light source and a single silicon chip that includes three or more detectors. Each detector is permanently coated by a different mix of dyes or other colorants that form a wavelength-selective filter. A single silicon chip embodies all the detectors and electronics, with each detector coated over by deposited filter layers.

1. A solid-state color-measuring device, comprising:
 at least one light source comprising a colorimeter illuminant for illuminating a sample; 
 a plurality of light detectors; and 
 a plurality of filters that are permanently deposited onto the solid-state color-measuring device, the filters being included in a plurality of layers such that light reflected off the sample passes through the layers and causes the plurality light detectors to cause the solid-state color-measuring device to produce an output having a plurality of colorimeter-illuminant-weighted spectral responses each approximating a reference-illuminant-weighted CIE-like color-matching function, 
 wherein a set of combinations of layers is determined, each of the combinations of layers being determined so that the output has the colorimeter-illuminant-weighted spectral responses that are linearly combined to approximate a set of reference-illuminant-weighted CIE-like color-matching functions; and further wherein one of the set of combinations is selected from a set of combinations having a best solution and meeting predetermined performance criteria, the combination that is selected being permanently deposited onto the solid-state color-measuring device. 
 
     
     
       2. The solid-state color-measuring device of  claim 1 , wherein the plurality of filters includes an infrared light filter. 
     
     
       3. The solid-state color-measuring device of  claim 1 , wherein the plurality of filters includes an ultraviolet light filter. 
     
     
       4. The solid-state color-measuring device of  claim 1 , wherein the solid-state color-measuring device is embedded in a color printer. 
     
     
       5. The solid-state color-measuring device of  claim 1 , wherein the solid-state color-measuring device operates in a fixed position with respect to the sample being measured. 
     
     
       6. The solid-state color-measuring device of  claim 1 , wherein the solid-state color-measuring device operates in a motion with respect to the sample being measured. 
     
     
       7. The solid-state color-measuring device of  claim 1 , wherein the plurality of light detectors is identical. 
     
     
       8. The solid-state color-measuring device of  claim 1 , wherein each of the plurality of filters has a thickness such that thickness of the plurality of filters in combination produce the output having the spectral responses approximating the illuminant-weighted CIE-like color-matching function. 
     
     
       9. The solid-state color-measuring device of  claim 1 , wherein each of the plurality of filters is permanently deposited onto a single one of the plurality of light detectors. 
     
     
       10. A colorimeter, comprising:
 at least one light source comprising a colorimeter illuminant for illuminating a sample; 
 a semiconductor substrate having four photodetectors; 
 four filters permanently deposited on the four photodetectors, wherein each of the four filters is included in a set of layers, wherein one of the four filters comprises a double layer and three of the four filters comprise single layers, and wherein the double layer is cyan and magenta and the single layers are, respectively, red, green, and yellow; and 
 a plurality of channels including the four photodetectors and the four filters so that particular linear combinations of a plurality of colorimeter-illuminant-weighted spectral responses of the plurality of channels each approximate a reference-illuminant-weighted CIE-like color-matching function. 
 
     
     
       11. The colorimeter of  claim 10 , wherein a thickness of each of the four filters is between about 0.50 microns and 2.00 microns. 
     
     
       12. The colorimeter of  claim 10 , wherein the semiconductor substrate has 64 photodetectors. 
     
     
       13. The colorimeter of  claim 10 , wherein the four filters are absorptive. 
     
     
       14. A system including the colorimeter of  claim 10 , wherein the system is a printer calibration system. 
     
     
       15. The colorimeter of  claim 10 , wherein the four filters include an infrared light filter. 
     
     
       16. The colorimeter of  claim 10 , wherein four filters include an ultraviolet light filter. 
     
     
       17. The colorimeter of  claim 10 , wherein the colorimeter is embedded in a color printer. 
     
     
       18. The colorimeter of  claim 10 , wherein the colorimeter operates in a fixed position with respect to the sample being measured. 
     
     
       19. The colorimeter of  claim 10 , wherein the colorimeter operates in motion with respect to the sample being measured. 
     
     
       20. The colorimeter of  claim 10 , wherein the four filters are integral with the four photodetectors.